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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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THE EARTHQUAKE ADVANCE THEORY         173
-ciers, and certainly in one, Black Glacier, there has been no advance, and probably will be none because of unfavorable conditions in the reservoirs. The fact that some of thelarger .glaciers, like the Seward and Hubbard, have not yet undergone transformation can hardly be due to this cause; and it is reasonably safe to predict a change for them also, when time enough has elapsed for the impulse to pass from their distant reservoirs, through the long valley ice streams to their fronts. When one of the large tidal glaciers responds the series will be complete for this region.
Elsewhere in Alaska there has been no analogous transformation of glaciers, so far AS can be learned. Such inquiry as we have been able to make reveals no evidence of recent notable change in the glaciers of southeastern Alaska with the exception of Glacier Bay; and our studies to the northwest of it, in the Copper River and Prince William Sound regions, and those of Professor Grant in the latter region and the Kenai Penin-.sula, fail to discover evidence of changes of like character in the glaciers of these sections. As is stated in the chapters describing our observations in Prince William Sound, there have been some recent changes in several of the glaciers, but nothing that compares •with the remarkable changes in the Yakutat Bay region. We feel warranted, therefore, in concluding that the spasmodic advance and absolute transformation of glaciers during the past 15 years is a phenomenon of Yakutat Bay and vicinity. That past changes of similar character may have occurred in other parts of Alaska seems probable; and it is believed possible that certain advances noticed in the Glacier Bay region, and elsewhere in Alaska, are similar in origin to the advance of the Yakutat Bay glaciers but with less intense cause, and consequently with less spectacular results.
An examination of the records of changes in glaciers in other regions has failed to discover either transformation or spasmodic advance by a group of glaciers of like nature to the phenomena of Yakutat Bay. There are many instances of forward movements succeeding periods of recession, and some of them have been spasmodic in their nature; but so far we have been unable to find anything comparable to the changes described in the preceding chapters. In this respect the glaciers of Yakutat Bay are unique among the glaciers of the world, so far as the literature which we have seen goes to show.
It is noteworthy, also, that in September, 1899, the Yakutat Bay region was the center of a series of earthquakes of great intensity; two or three of them ranking with the greatest of recent earthquakes.1 For three weeks the region was repeatedly shaken, and there were hundreds of shocks in all. In our reports upon these earthquakes abundant evidence has been presented to prove that during the earthquakes there were frequent and enormous avalanches of snow, ice, and rock. These avalanches have not only been testified to by prospectors encamped within Disenchantment Bay during the 'earthquakes, who saw and heard them fall, by the natives who report that certain mountain faces were "completely changed" by the earthquakes, but by our own observation of exceedingly abundant, fresh avalanche scars upon the mountains, far more abundant than in other mountain regions of Alaska that were not severely shaken during these 'earthquakes. Comparison of photographs taken before the 1899 earthquakes with those taken after it show conclusively what large areas of avalanches there were in those places.
> Tarr, R. S. and Martin, Lawrence, Recent Changes of Level in the Yakutat Bay Region, Alaska, Bull. Geol. Soc. Amer., Vol. 17,1906, pp. 29-64; Geog. Journ., Vol. XXVIII, 1906, pp. 30-42; The Earthquakes at Yakutat Bay, Alaska, in September, 1899, Professional Paper 69, U. S. Geol. Survey, 1912; Martin, Lawrence. The Alaskan Earthquakes of 1899, Bull. Geol. Soc. Amer., Vol. XXI, 1910, pp. 339-406.